We measured vapor-liquid equilibria (VLE) for the system of pentafluoroethane (HFC12)-difluoroethane (HFC152a) over the temperature range from 268.15 K to 373.15 K. Fitting VLE data obtained to an extended BWR equation of state, binary interaction parameters were correlated as a linear function of temperature. Applying the equation of state including the binary interaction parameters to refrigeration cycle, estimation of coefficient of performance (COP) revealed about 13.3% energy-saving against chlorodifluoromethane (HCFC22), when the mole fraction of HFC125 is 0.44. As the condition of COP estimation, we assumed that temperature changes of out-side fluids were from 285.15 down to 280.15 K and 305.15 up to 310.15 K with 3 K in minimum temperature difference, respectively.